The first man-made plastic was invented in Britain in 1851 by Alexander PARKES. He publicly demonstrated it at the 1862 International Exhibition in London, calling the material Parkesine. Derived from cellulose, Parkesine could be heated, molded, and retain its shape when cooled. It was, however, expensive to produce, prone to cracking, and highly flammable. In 1868, American inventor John Wesley HYATT developed a plastic material he named Celluloid, improving on PARKES' invention so that it could be processed into finished form. HYATT patented the first injection molding machine in 1872. It worked like a large hypodermic needle, using a plunger to inject plastic through a heated cylinder into a mold. The industry expanded rapidly in the 1940s because World War II created a huge demand for inexpensive, mass-produced products. In 1946, American inventor James Watson HENDRY built the first screw injection machine. This machine also allowed material to be mixed before injection, so that colored or recycled plastic could be added to virgin material and mixed thoroughly before being injected. In the 1970s, HENDRY went on to develop the first gas-assisted injection molding process.
Injection molding machines consist of a material hopper, an injection ram or screw-type plunger, and a heating unit. They are also known as presses, they hold the molds in which the components are shaped. Presses are rated by tonnage, which expresses the amount of clamping force that the machine can exert. This force keeps the mold closed during the injection process. Tonnage can vary from less than 5 tons to 6000 tons, with the higher figures used in comparatively few manufacturing operations. The total clamp force needed is determined by the projected area of the part being molded. This projected area is multiplied by a clamp force of from 2 to 8 tons for each square inch of the projected areas. As a rule of thumb, 4 or 5 tons per square inch can be used for most products. If the plastic material is very stiff, it will require more injection pressure to fill the mold, thus more clamp tonnage to hold the mold closed. The required force can also be determined by the material used and the size of the part, larger parts require higher clamping force. With Injection Molding, granular plastic is fed by gravity from a hopper into a heated barrel. As the granules are slowly moved forward by a screw-type plunger, the plastic is forced into a heated chamber, where it is melted. As the plunger advances, the melted plastic is forced through a nozzle that rests against the mold, allowing it to enter the mold cavity through a gate and runner system. The mold remains cold so the plastic solidifies almost as soon as the mold is filled.
Mold assembly or die are terms used to describe the tooling used to produce plastic parts in molding. The mold assembly are used in mass production where thousands of parts are produced. Molds are typically constructed from hardened steel, etc.
U.S. Pat. No. 5,795,511 (Inventor: KALANTZIS, et al.; Filed: 6 Jun. 1995) discloses an apparatus and method for providing material to a mold, such as in an injection molding system, wherein the settings for controlling the molding operation are retained in a non-volatile memory in a hot-half of the mold.
European patent Number 0967063 (Inventor: Moss et al.; Filed: 24 Jun. 1999) discloses a pressure transducer used to sense the pressure in the manifold bore downstream of the valve pin head.
U.S. Pat. No. 6,000,831 (Inventor: TRIPLETT; Filed: 14 Dec. 1999) discloses injection mold hot runner control devices and more particularly to an injection molding control device which eliminates the conventional control cables to improve the quality of feedback signals received by the controller and the safety of the environment in which such systems are used.
U.S. Pat. No. 6,529,796 (Inventor: Kroeger, et al.; Filed: 21 Jul. 1999) discloses an injection mold apparatus having multiple injection zones, each zone having at least one heater and at least one temperature sensor generating a temperature indicating signal.
U.S. Pat. No. 6,421,577 (Inventor: TRIPLETT; Filed: 15 Oct. 1999) discloses injection mold hot runner control devices and more particularly to an injection molding control device which eliminates the conventional control cables to improve the quality of feedback signals received by the controller and the safety of the environment in which such systems are used.
U.S. Pat. No. 6,589,039 (Inventor: DOUGHTY et al.; Filed: 2000-10-30) discloses a system and method in which the rate of material flow to a plurality of gates can be controlled by a single controller.
United States Patent Publication Number 20030154004 (Inventor: KROEGER, et al.; Filed: 23 Jan. 2003) discloses an injection mold apparatus having multiple injection zones, each zone having at least one heater and at least one temperature sensor generating a temperature indicating signal.
U.S. Pat. No. 7,214,048 (Inventor: KIM; Filed: 25 May 2004) discloses control for a valve pin through a linear motor controlled by a pulse signal and through a cooling block, so that an opening/closing amount of a gate can be precisely managed.
U.S. Pat. No. 7,258,536 (Inventor: OLARU, et al.; Filed: 21 Jun. 2004) discloses a control module attached to a machine platen of an injection molding machine. The control module is coupled to at least one sensor that reports a value of a processing condition associated with an injection mold and is disposed within the injection mold. The control module is also coupled to at least one controllable device that varies the processing condition of the injection mold and is disposed within the injection mold. The control module collects and processes sensor output, and provides a control signal to at least one controllable device. A display interface module is linked to the control module. The display interface module accepts user-entered data set-points, provides the user-entered data set-points to the control module, and collects the processed sensor output from the control module for display to a user.
United States Patent Publication Number 20060082009 (Inventor: Quail, et al; Filed: 19 Oct. 2004) discloses an intelligent molding system that makes use of data directly associated with a molding environment or particular mold.
United States Patent Publication Number 2008/0290541 (Inventor: BAUMANN; Filed: 25 May 2007) discloses an injection molding system including a hot runner comprising a memory device configured to contain at least one process control parameter.
United States Patent Publication Number 2008/0006955 (Inventor: NIEWELS; filed: 5 Jul. 2007) discloses a piezoceramic actuator actuated so as to supply the force to seal the side acting core insert against the core insert during a molding operation. Sensors are used to detect pressure between mold components and to transmit sense signals to a controller.